The present invention relates generally to a method and system for analyzing insulative structures with radar. More particularly, the invention relates to a method and system for detecting and characterizing anomalies in wooden utility poles and related insulative component structures.
The power-utility-system infrastructure alone in North America includes approximately 150,000,000 wooden pole structures. A similarly large number of wooden poles are additionally used by the telecommunications industry. Wood remains valuable as a material for constructing power and telecommunications poles because of its cost effectiveness and reasonable durability. Such poles are, nevertheless, subject to deterioration over time, not only from climatic effects, but also from biological and mechanical assaults. For example, biological deterioration may result from the activity of decay fungi, wood-boring insects, or birds. Woodpeckers have been known to bore vertical tunnels in wooden poles greater than twelve feet in length. Mechanical damage can result from such things as vehicular collisions or shotgun impacts. Consequently, each wooden pole in the system must be inspected periodically and a determination made whether to replace the pole based on the strength of the pole. Typically, poles are inspected on a 5-9 year cycle.
Various methods currently exist for evaluating pole strength, generally requiring direct physical contact with the pole. Such methods rely primarily on sampling techniques in which the strength of the pole is deduced from an assessment of its characteristics at the sampled points. Such sampling is typically performed in the region of the pole easily accessible by a technician, i.e. between about six feet above the ground to about two feet below the ground, so that only about 10% of the pole is even within the sampling region. Crossarms, which are positioned near the tops of the poles, are rarely examined for deterioration. Current methods also tend to include significant reliance on the qualitative assessment of the technician examining the pole. Individual visits to every pole to perform the inspection additionally result in substantial costs for maintaining the pole infrastructures.
In addition to the functional integrity of the utility pole being dependent on the structural soundness of the wooden pole and crossarm structures, it may also depend on the condition of other insulative pole structures. For example, many utility poles are equipped with xe2x80x9cinsulators,xe2x80x9d which are knobs that are affixed to the poles, usually on the crossarms, and are used to support the utility lines. The insulators may be fabricated of appropriate insulative material, such as rubber, fiberglass, ceramic, or porcelain. The insulators are also exposed to weather and biological deterioration that may adversely affect their performance. In some cases, cracks may form in the insulators and later be filled with water or metal. The change in electrical character may result in flashover, which may trip circuitry and in some cases cause a fire that burns the wooden crossarm, or causes even greater damage.
There is accordingly room for improving the reliability of wooden-pole deterioration measurements by examining substantially the entirety of the structures and automating the evaluation of their strength. In addition, the cost for assessing the structures can be reduced by using a system that eliminates the need to have each pole visited individually.
Thus, embodiments of the invention are directed to a method and system for analyzing insulative structures. In certain embodiments, a wooden structure, such as a utility or telecommunications pole, is analyzed, while in other embodiments the invention is more generally applicable to other insulative components of structures.
In embodiments directed to the analysis of a wooden structure, a location for the wooden structure is identified. A first radar signal is propagated towards the wooden structure with a radar antenna while the radar antenna is motion along a navigation path in the vicinity of the wooden structure. A reflected radar signal is received from the wooden structure, from which a determination is made whether the wooden structure contains a structural anomaly. The wooden structure may be identified by imaging the wooden structure, such as with a charge coupled device or infrared camera. In certain embodiments, longitude and latitude positions for the wooden structure are ascertained with a global positioning system. The location of the wooden structure may also be identified by reflecting a laser signal from it.
In various embodiments, a second radar signal modulated in accordance with a pulse compression scheme is propagated towards the wooden structure. The first and second radar signals may be provided by the same radar subsystem or by separate radar subsystems in different embodiments. The determination of whether the wooden structure contains a structural anomaly may be made in one embodiment from data extracted from the reflected radar signal by calculating a density distribution for the wooden structure. The calculated density distribution may be used to designate closed-volume regions within the wooden structure having a density less than a threshold density relative to a mean density for the structure thereby identifying them as possible structural anomalies.
Other embodiments of the invention are directed to identifying an anomaly in an insulative component of a structure. In such embodiments, a location for the structure and a position for the insulative component relative to the structure are identified. A first radar signal is propagated towards the insulative component with a radar antenna while the radar antenna is in motion along a navigation path in the vicinity of the structure. A reflected radar signal in received, from which it is determined whether the insulative component contains the anomaly. Various aspects of the invention used for the analysis of wooden structures may also be incorporated in the identification of anomalies in insulative components. In particular, propagating a second radar signal modulated in accordance with a pulse compression scheme may be performed such that the reflected radar signal includes signal components originating from both the first and second radar signals.